The present invention relates to a relief valve, in particular to a relief valve for releasing a boost pressure of a turbocharger.
In order to meet increasingly stringent requirements on exhaust emissions of motor vehicles and on the reduction of fuel consumption, actuators for the engine control, e.g. a relief valve of that kind, have to respond to a corresponding actuating signal as fast and precisely as possible. However, this requirement is aggravated by the fact that a spring for closing such a relief valve has to apply a high force in order to keep the valve closed against the incoming dynamic pressure of the turbocharger.
In order to overcome this disadvantage, the laid-open publication DE 102 48 125 A1 suggests a so-called balanced valve in which fluid passageways are disposed in a valve body in order to apply the incoming fluid pressure also to the backside of the valve body. The backside of the valve body is sealed via a membrane. Thus, since the compressive force is the same on each side of the valve body, a weaker spring and a weaker actuator may be built in.
Patent document DE 10 2004 044 439 B4 suggests a relief valve for a turbocharger with a lip-shaped sealing element for sealing a backside of the valve body when the valve body is closed, so that a fluid force acting on the backside of the valve body keeps the valve body closed while the fluid pressure acting on the backside is released via a radial annular clearance of the sealing element 4 when the valve opens, in order to open the valve body by the incoming dynamic pressure on a face of the valve body. The lip-shaped sealing element has a larger effective diameter than a seal seat of the valve body, so that excess force is generated in a closing direction, which is used to keep the valve closed.